Method and system for video picture intra-prediction estimation

ABSTRACT

Several systems and methods for intra-prediction estimation of video pictures are disclosed. In an embodiment, the method includes accessing four ‘N×N’ pixel blocks comprising luma-related pixels. The four ‘N×N’ pixel blocks collectively configure a ‘2N×2N’ pixel block. A first pre-determined number of candidate luma intra-prediction modes is accessed for each of the four ‘N×N’ pixel blocks. A presence of one or more luma intra-prediction modes that are common among the candidate luma intra-prediction modes of at least two of the four ‘N×N’ pixel blocks is identified. The method further includes performing, based on the identification, one of (1) selecting a principal luma intra-prediction mode for the ‘2N×2N’ pixel block and (2) limiting a partitioning size to a ‘N×N’ pixel block size for a portion of the video picture corresponding to the ‘2N×2N’ pixel block.

This application is a continuation of U.S. patent application Ser. No.15/043,973, filed Feb. 15, 2016, which is a continuation of U.S. patentapplication Ser. No. 13/936,249 filed Jul. 8, 2013, which claims thebenefit of U.S. Provisional Application No. 61/668,748, filed Jul. 6,2012, the entire contents of all being incorporated by reference herein.

TECHNICAL FIELD

The present disclosure generally relates to the field ofintra-prediction estimation in video pictures.

BACKGROUND

Technological advancements over time have enabled video pictures to becaptured at higher resolutions along with a corresponding increase invideo data picture size. Accordingly, video pictures may be compressed(e.g. encoded) by exploiting spatial and/or temporal redundanciestherein in order to efficiently utilize a storage space or efficientlyutilize bandwidth during a transmission. The compression of videopictures, typically, includes predicting blocks of pixels correspondingto a video picture from other pixel blocks within the same video picture(e.g. intra-prediction) or from pixel blocks from one or more referencevideo pictures (e.g. inter-prediction). Video coding standards, such as,for example, high efficiency video coding (HEVC) suggest a number ofintra-prediction modes for facilitating intra-prediction, where eachintra-prediction mode corresponds to a direction of prediction. As aresult of variable prediction unit size and quad-tree complexity,selecting an intra-prediction mode for a pixel block from among thesuggested intra-prediction modes is computationally intensive, therebyleading to increased resource and power utilization.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key or essentialfeatures of the claimed subject matter, nor is it intended to be used asan aid in determining the scope of the claimed subject matter.

Various systems, methods, and computer-readable mediums configured forvideo picture intra-prediction estimation are disclosed. In anembodiment, the method includes accessing four ‘N×N’ pixel blocks by anintra-prediction estimation device. In an embodiment, the four ‘N×N’pixel blocks comprise luma-related pixels, and the four ‘N×N’ pixelblocks collectively configure a ‘2N×2N’ pixel block of a video picture.In an embodiment, ‘N’ is an integer value with value from one among 8,16 and 32. The method further includes accessing a first pre-determinednumber of candidate luma intra-prediction modes for each of the four‘N×N’ pixel blocks by the intra-prediction estimation device. In anembodiment, a candidacy of the luma intra-prediction modes is determinedbased on a predefined measure. In an embodiment, the predefined measureis one of a sum of absolute differences (SAD) cost and a sum of absolutetransform differences (SATD) cost. The method further includesidentifying, with the intra-prediction estimation device, a presence ofone or more luma intra-prediction modes that are common among thecandidate luma intra-prediction modes of at least two of the four ‘N×N’pixel blocks. The method also includes performing, by theintra-prediction estimation device, one of (1) selecting a principalluma intra-prediction mode for the ‘2N×2N’ pixel block from among theone or more luma intra-prediction modes based on identifying thepresence of the one or more luma intra-prediction modes that are commonamong the candidate luma intra-prediction modes of at least two of thefour ‘N×N’ pixel blocks, and (2) limiting a partitioning size to a ‘N×N’pixel block size for a portion of the video picture corresponding to the‘2N×2N’ pixel block subsequent to identifying an absence of the one ormore luma intra-prediction modes that are common among the candidateluma intra-prediction modes of at least two of the four ‘N×N’ pixelblocks.

In an embodiment, if a presence of a luma intra-prediction mode fromamong the one or more luma intra-prediction modes that is common to eachof the four ‘N×N’ pixel blocks is identified, then the lumaintra-prediction mode is selected as the principal luma intra-predictionmode for the ‘2N×2N’ pixel block. In an embodiment, that are commonamong the candidate luma intra-prediction modes of two or three ‘N×N’pixel blocks from among the four ‘N×N’ pixel blocks is identified, thenthe intra-prediction estimation device is configured to (1) associatethe one or more luma intra-prediction modes with the remaining pixelblocks from among the four ‘N×N’ pixel blocks (2) compute RDO cost foreach of one or more luma intra-prediction modes for each of theremaining pixel blocks, and (3) select a luma intra-prediction mode fromamong the one or more luma intra-prediction modes as the principal lumaintra-prediction mode for the ‘2N×2N’ pixel block based on the RDO costassociated with each of the one or more luma intra-prediction modes.

In an embodiment, the method further includes accessing four pixelblocks comprising chroma-related pixels by the intra-predictionestimation device. The four pixel blocks collectively configure a chromapixel block corresponding to the ‘2N×2N’ pixel block. The method furtherincludes accessing a second pre-determined number of candidate chromaintra-prediction modes for each of the four pixel blocks by theintra-prediction estimation device, where a candidacy of the chromaintra-prediction modes being determined based on the predefined measure.A presence of one or more chroma intra-prediction modes that are commonfrom among the candidate chroma intra-prediction modes of at least twoof the four pixel blocks is identified and a principal chromaintra-prediction mode is selected for the chroma pixel block based onidentifying the presence of the one or more chroma intra-predictionmodes. In an embodiment, a presence of the principal lumaintra-prediction mode for the ‘2N×2N’ pixel block from among the one ormore chroma intra-prediction modes is identified by the intra-predictionestimation device, wherein the presence of principal lumaintra-prediction mode is identified subsequent to identifying thepresence of one or more chroma intra-prediction modes from among thecandidate chroma intra-prediction modes.

Additionally, in an embodiment, a system for video pictureintra-prediction estimation is provided. The system includes a memorydevice and an intra-prediction estimation device communicativelyassociated with the memory device. The memory device is configured tostore one or more video pictures. The intra-prediction estimation deviceis configured to access four ‘N×N’ pixel blocks from the memory device.In an embodiment, the four ‘N×N’ pixel blocks comprise luma-relatedpixels, and the four ‘N×N’ pixel blocks collectively configure a ‘2N×2N’pixel block of a video picture from among one or more video pictures. Inan embodiment, ‘N’ is an integer value with value from one among 8, 16and 32. The intra-prediction estimation device is further configured toaccess a first pre-determined number of candidate luma intra-predictionmodes for each of the four ‘N×N’ pixel blocks. In an embodiment, acandidacy of the luma intra-prediction modes is determined based on apredefined measure. The intra-prediction estimation device is configuredto identify a presence of one or more luma intra-prediction modes thatare common among the candidate luma intra-prediction modes of at leasttwo of the four ‘N×N’ pixel blocks. The intra-prediction estimationdevice is configured to perform one of (1) selecting a principal lumaintra-prediction mode for the ‘2N×2N’ pixel block from among the one ormore luma intra-prediction modes based on identifying the presence ofthe one or more luma intra-prediction modes that are common among thecandidate luma intra-prediction modes of at least two of the four ‘N×N’pixel blocks, and (2) limiting a partitioning size to a ‘N×N’ pixelblock size for a portion of the video picture corresponding to the‘2N×2N’ pixel block subsequent to identifying an absence of the one ormore luma intra-prediction modes that are common among the candidateluma intra-prediction modes of at least two of the four ‘N×N’ pixelblocks.

Moreover, in an embodiment, a non-transitory computer-readable mediumstoring a set of instructions that when executed cause a computer toperform a method for intra-prediction estimation of video pictures isdisclosed. In an embodiment, the method includes accessing four ‘N×N’pixel blocks. In an embodiment, the four ‘N×N’ pixel blocks compriseluma-related pixels, and the four ‘N×N’ pixel blocks collectivelyconfigure a ‘2N×2N’ pixel block of a video picture. In an embodiment,‘N’ is an integer value with value from one among 8, 16 and 32. Themethod further includes accessing a first pre-determined number ofcandidate luma intra-prediction modes for each of the four ‘N×N’ pixelblocks. In an embodiment, a candidacy of the luma intra-prediction modesis determined based on a predefined measure. In an embodiment, thepredefined measure is one of a SAD cost and a SATD cost. The methodfurther includes identifying, a presence of one or more lumaintra-prediction modes that are common among the candidate lumaintra-prediction modes of at least two of the four ‘N×N’ pixel blocks.The method also includes performing one of (1) selecting a principalluma intra-prediction mode for the ‘2N×2N’ pixel block from among theone or more luma intra-prediction modes based on identifying thepresence of the one or more luma intra-prediction modes that are commonamong the candidate luma intra-prediction modes of at least two of thefour ‘N×N’ pixel blocks, and (2) limiting a partitioning size to a ‘N×N’pixel block size for a portion of the video picture corresponding to the‘2N×2N’ pixel block subsequent to identifying an absence of the one ormore luma intra-prediction modes that are common among the candidateluma intra-prediction modes of at least two of the four ‘N×N’ pixelblocks.

Other aspects and example embodiments are provided in the drawings andthe detailed description that follows.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a simplified overview of an exemplary process flowfor encoding of video pictures in accordance with an example scenario;

FIG. 2 is a simplified block diagram of an exemplary system configuredfor video picture intra-prediction estimation in accordance with anembodiment;

FIG. 3 depicts an exemplary visual representation of four ‘32×32’ lumablocks for illustrating a selection of a principal luma intra-predictionmode for a ‘64×64’ luma block in accordance with an embodiment;

FIG. 4 depicts an exemplary visual representation of four ‘16×16’ chromablocks for illustrating a selection of a principal chromaintra-prediction mode for a ‘32×32’ chroma block in accordance with anembodiment;

FIGS. 5A and 5B illustrate a flow diagram of an exemplary method of lumaintra-prediction estimation in accordance with an embodiment;

FIGS. 6A and 6B illustrate a flow diagram of an exemplary method ofchroma intra-prediction estimation in accordance with an embodiment; and

FIG. 7 is a block diagram of an exemplary integrated circuit configuredto facilitate video picture intra-prediction estimation in accordancewith an embodiment.

The drawings referred to in this description are not to be understood asbeing drawn to scale except if specifically noted, and such drawings areonly exemplary in nature.

DETAILED DESCRIPTION

Pursuant to an example scenario, video pictures constituting video dataare compressed (e.g. encoded) to efficiently utilize a storage capacityduring storage or a spectrum/bandwidth during a transmission. Anexemplary encoding of a video picture is explained with reference toFIG. 1.

FIG. 1 illustrates a simplified overview of an exemplary process flow100 for encoding of a video picture 102 in accordance with an examplescenario. Pursuant to an exemplary scenario, a video encoder may performthe process flow 100 to achieve the compression of the video picture102. The video picture 102 may be compressed so as to efficientlyutilize a storage capacity during storage or a spectrum/bandwidth duringa transmission. The video encoder may be configured within a multimediasystem. Examples of the multimedia system may include, but are notlimited to, (1) multimedia devices, such as cellular phones, digitalvideo cameras and digital camcorders; (2) data processing devices, suchas personal computers, laptops and personal digital assistants; and (3)consumer electronics, such as set top boxes, digital video disk (DVD)players and video network servers. Pursuant to an exemplary scenario,the video encoder may be any machine capable of executing a set ofinstructions (sequential and/or otherwise) so as to perform an encodingof video pictures, such as the video picture 102.

Video data comprising a plurality of video pictures, such as the videopicture 102, may be received by the video encoder from a media capturedevice. Examples of a media capture device may include a video camera ora camcorder. The media capture device may be, for example, a stand-alonedevice or a part of a mobile device, such as a Smartphone, or a dataprocessing device, such as a personal computer, a laptop device or apersonal digital assistant (PDA). The video picture 102 may also bereceived by the video encoder from a transcoding system (implemented inany of hardware, software or firmware), which may be stand-alone deviceor a part of media capture device.

Pursuant to an exemplary scenario, the video picture 102 is composed ofseveral blocks of pixels (also referred to hereinafter as pixel blocks).Accordingly, the video picture 102 is processed in units of pixelblocks. It is noted that the term ‘pixel blocks’ as used herein may be ageneralized term for the term ‘largest coding units (LCU)’ (or codingunits) as defined in high efficiency video coding (HEVC) standard or theterm ‘macroblocks’ according H.264/MPEG-4 advanced video codingstandard. A prediction for a pixel block being processed (e.g. a currentblock) of the video picture 102 is performed based on previously encodedpixel blocks either from the video picture 102 itself (e.g.,intra-prediction) or from pixel blocks from other video pictures thathave already been encoded and transmitted (e.g., inter prediction).Identifying a suitable inter-prediction is referred to as motionestimation and subtracting the inter-prediction from the current blockis referred to as motion compensation. Accordingly, the process flow 100includes a loop for performing inter-prediction based on reference videopictures 104 and a separate loop for performing intra-prediction. Theinter-prediction loop includes performing motion estimation of thecurrent block at 106 followed by motion compensation at 108.Alternatively, the current block may be subjected to intra-prediction bychoosing intra-prediction at 110 followed by performing intra-predictionat 112. The process flow 100 includes a switch 114, which performsselection of one of the loops from among those associated withinter-prediction or intra-prediction. Pursuant of an exemplary scenario,a cost (in terms of peak signal to noise ratio (PSNR) and/or bit-rate)of performing inter-prediction or intra-prediction is computed todetermine the selection of the appropriate loop. In an embodiment, anavailability of reference video pictures (for example, in case ofI-pictures) is also be taken into account while selecting theappropriate loop from among those associated with inter-prediction orintra-prediction.

Subsequent to performing one of intra-prediction or inter-predictionestimation, a prediction ‘P’ corresponding to the current block isgenerated. The prediction ‘P’ is subtracted from the current block ofthe video picture 102 at 116 to generate a residual ‘R’. The residual‘R’ is subjected to transformation at 118 and quantization at 120. Thetransformation of the residual ‘R’ outputs a set of transformcoefficients, each of which is a weighting value for a standard basispattern. The weighted basis patterns, when combined, are capable ofre-creating the residual ‘R’. The set of transform coefficients are thenquantized (such as where each coefficient is scaled corresponding to ascale-down factor which may be a mathematical reciprocal of the scale-upfactor specified by a video coding standard, effectively setting anumber of transform coefficients to a small value (including zerovalue)) to achieve compression.

The quantized transform coefficients, along with certain information(for example, information such as: information about the structure ofcompressed data, information about a complete sequence of video dataand/or information that enables a decoder to re-create the prediction),are subject to entropy encoding (e.g., conversion into binary codesusing variable length coding and/or arithmetic coding) at 122. Theentropy encoding of pixel blocks, such as the current block,corresponding to the video picture 102 produces an efficient, compactbinary representation of the information in the form of encoded videopicture 124. The encoded video picture 124 may then be stored and/ortransmitted to a digital system including a decoder capable of decodingthe encoded video picture 124. It is noted that the decoder may beconfigured to perform a decoding process flow, which generally suggestsperforming the inverse of the operations of process flow 100 in reverseorder to decompress, e.g., decode, a compressed video sequence. Thedecoding process flow is not explained herein for sake of brevity.

The process flow 100 further includes a reconstruction loop, whereintransformed and quantized residual ‘R’ is subjected to de-quantization(e.g., scaled corresponding to a scale-up factor which may be, in anexample embodiment, a value specified by a multimedia standard) at 126and then inverse transformation at 128 to obtain the reconstructedresidual ‘RR’. At 130, the reconstructed residual ‘RR’ data is then beadded (e.g., combined) with prediction ‘P’ corresponding to the currentblock to generate reconstructed current block.

The reconstructed current block is be utilized for intra-prediction ofnext pixel blocks within the video picture 102. The reconstructedcurrent block(s) is also be filtered (for example, using a deblockingfilter) at 132 and stored in the reference frame buffer at 134. In anembodiment, the filtering may be performed, for example, on a pixelblock-by-pixel block basis or on a picture basis. This filtering isperformed to improve the reference pictures used for encoding/decodingof subsequent pictures. For example, an in-loop filter component may,for example, adaptively apply low-pass filters to block boundariesaccording to the boundary strength to alleviate blocking artifactscaused by the block-based video coding. The stored reconstructed pixelblocks, such as the reconstructed current block, constituting an entirevideo picture are then be utilized as reference video pictures at 104for inter-prediction of video pictures subsequent to the video picture102 in a video data sequence.

As can be seen from the process flow 100, prediction (e.g.intra-prediction or intra-prediction) of pixel blocks drives the latterstages of the encoding process, such as transformation, quantization andentropy encoding. Accordingly, the prediction has to be performed in afairly accurate and efficient manner. The video coding standard HEVCsuggests a number of intra-prediction modes (e.g. directions ofpredictions) to this effect. For example, HEVC suggests 35intra-prediction modes for facilitating a prediction of a luminancecomponent (hereinafter referred to as luma). Determining a suitableintra-prediction mode for each pixel block by evaluating each of the 35intra-prediction modes (for example, by performing a rate distortionoptimization (RDO) cost determination for each intra-prediction mode) iscomputationally expensive. Accordingly, a difference measure, such assum of absolute differences (SAD) cost or sum of absolute transformdifferences (SATD) cost may be computed for each of the 35intra-prediction modes for a pixel block and a small set ofintra-prediction modes may be identified from among the 35intra-prediction modes based on minimization of SAD/SATD cost. A RDOcomputation may be performed for only this small set of intra-predictionmodes to identify the principal luma intra-prediction mode for the pixelblock. Performing the intra-prediction estimation in such a manner,though reducing a number of computations, does not suggest re-usingblock computations for subsequent blocks. Further, on account ofvariable block size and quad tree complexity in HEVC standard, theintra-prediction estimation is still computationally intensive. Variousembodiments of the present technology, however, provide methods,systems, and computer-readable mediums for performing video pictureintra-prediction estimation that are capable of overcoming these andother obstacles and providing additional benefits. A system configuredto perform intra-prediction estimation is described herein withreference to FIG. 2.

FIG. 2 is a simplified block diagram of an example system 200 configuredfor performing video picture intra-prediction estimation in accordancewith an embodiment. In an embodiment, the system 200 may be includedwithin a video processing device with or without the capability of videoplayback. Examples of the video processing device include, but are notlimited to: (1) multimedia device, such as, for example, a cellularphone, a digital video camera and a digital camcorder; (2) dataprocessing device, such as, for example, a personal computer (PC), alaptop, a tablet PC, and a personal digital assistants; and (3) consumerelectronics, such as, for example, a set top box, a digital video disk(DVD) player and a video network server. In another embodiment, thesystem 200 may be configured to be included within a videoencoder/decoder (hereinafter referred to as a video codec). Pursuant toan example scenario, the video codec may be any machine capable ofexecuting a set of instructions (sequential and/or otherwise) so as toperform an encoding and decoding of video data. For example, the system200 may be included within a video codec configured to execute theprocess flow 100 of FIG. 1. In an embodiment, the video codec may beconfigured within a video processing device. Alternatively, in anembodiment, the system 200 may be communicatively associated with orcoupled to a video codec such that intra-prediction estimation of pixelblocks corresponding to the video picture may be performed and thecorresponding output may be provided to the video codec. In anembodiment, the system 200 may be configured within a video contentanalysis (VCA) system.

In FIG. 2, the system 200 is depicted to include a memory device 202 andan intra-prediction estimation device 204. The intra-predictionestimation device 204 is hereinafter referred to as IPE device 204. TheIPE device 204 may be included within the ‘intra-prediction’ component112 in the process flow 100 of FIG. 1. The memory device 202 isconfigured to store one or more video pictures, such as the videopicture 102 depicted in process flow 100 of FIG. 1. In cases where thesystem 200 is included within a video codec, the memory device 202 mayrefer to an internal buffer (temporary or otherwise) which iscommunicably associated with an internal storage associated with a videoprocessing device housing the video codec. Examples of the memory device202 include, but are not limited to, a random access memory (RAM), asynchronous dynamic RAM (SDRAM), a double data rate SDRAM (DDR SDRAM),and the like. It is noted that the system 200 may include a plurality ofcomponents configured to facilitate various functions ofencoding/decoding of video pictures and which are not depicted herein inFIG. 2 for sake of brevity. The memory device 202 and the IPE device 204are communicatively associated with each other as depicted in FIG. 2.The communication between the memory device 202 and the IPE device 204may be facilitated by various means, such as data bus, control bus andthe like. The bus may be, for example, a serial bus, a unidirectionalbus or a bi-directional bus.

The IPE device 204 includes a cost computation module 206, a comparisonmodule 208 and a decision module 210. The various modules of the IPEdevice 204, such as the cost computation module 206, the comparisonmodule 208 and the decision module 210 are communicably associated witheach other via bus 212. Examples of the bus 212 include, but are notlimited to, a data bus, an address bus, a control bus, and the like. Thebus 212 may be, for example, a serial bus, a bi-directional bus or aunidirectional bus. Further, the various modules of the IPE device 204,such as the cost computation module 206, the comparison module 208 andthe decision module 210 may be implemented as hardware, software,firmware or any combination thereof.

In an embodiment, the IPE device 204 may be embodied as a multi-coreprocessor, a single-core processor, or a combination of one or moremulti-core processors and one or more single-core processors. Forexample, the IPE device 204 may be embodied as one or more of variousprocessing devices, such as a coprocessor, a microprocessor, acontroller, a digital signal processor (DSP), processing circuitry withor without an accompanying DSP, or various other processing devicesincluding integrated circuits such as, for example, an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA), a microcontroller unit (MCU), a hardware accelerator, aspecial-purpose computer chip, or the like. In an embodiment, the IPEdevice 204 may be configured to execute hard-coded functionality. In anembodiment, the IPE device 204 may be embodied as an executor ofsoftware instructions, wherein the instructions may specificallyconfigure the IPE device 204 to perform the algorithms and/or operationsdescribed herein when the instructions are executed. The IPE device 204may include, among other things, a clock, an arithmetic logic unit (ALU)and logic gates configured to support an operation of the IPE device204. In an embodiment, the IPE device 204 may be an advanced reducedinstruction set computer (RISC) machine (ARM) processor.

In an embodiment, the cost computation module 206 is configured tocompute one or more costs associated with pixel blocks of a videopicture, such as the video picture 102 of FIG. 1. In an embodiment, thecost computation module 206 is configured to compute a SAD cost forpixel blocks associated with the video picture. A SAD cost refers to asum value of absolute differences in pixel values between a pixel blockand a corresponding predicted pixel block. Accordingly, a higher SADcost may imply a higher amount of difference between the pixel block andthe corresponding predicted pixel block (e.g. a larger residual) therebyrequiring higher number of bits for encoding the pixel block. In anembodiment, the cost computation module 206 is configured to compute aSATD cost for the pixel blocks associated with the video picture. A SATDcost refers to a sum value of absolute transform differences between apixel block and a corresponding predicted pixel block.

In an embodiment, the cost computation module 206 is also configured tocompute RDO cost for pixel blocks associated with the video picture. Invideo coding standards such as the HEVC, multiple intra-prediction modesare suggested for intra-prediction of pixel blocks. Accordingly, a cost(in terms of peak-signal to noise ratio (PSNR) and bit rate) of usingeach intra-prediction mode is determined and the intra-prediction modewith the minimum RDO cost is chosen as the principal intra-predictionmode for the pixel block. It is noted that the term ‘principal’intra-prediction mode (for luma or chroma components) as used hereinrefers to the most preferred mode for performing the saidintra-prediction for a pixel block. An RDO cost computation involvesapproximating the process flow 100 of FIG. 1 within the IPE device 204and forecasting a bit rate (for example, bit rate obtained after entropyencoding) and a PSNR (obtained from reconstructed pixel block) that maybe achieved upon utilization of a selected intra-prediction mode. In anembodiment, the cost computation module 206 is configured to compute theRDO costs for various suggested intra-prediction modes and provide theresults to the comparison module 208. The comparison module 208 comparesthe RDO costs for various intra-prediction modes and provides an outputto the decision module 210, which determines the principalintra-prediction mode (e.g. a mode with least RDO cost) based on thecomparison of RDO costs.

In an embodiment, the cost computation module 206 is also configured todetermine a partitioning cost of partitioning portions within a videopicture. For example, the cost computation module 206 is configured todetermine a partitioning cost of partitioning portions within a LCU intoone or more configurations of prediction units (PUs). For example, apartitioning cost for each ‘4×4’, ‘8×8', ‘16×16’, ‘32×32’ and ‘64×64’PUs is computed and compared (for example, by the comparison module 208)to enable the decision module 210 to determine the partitioning size foreach LCU portion. For example, cost of partitioning a LCU portion intofour ‘4×4’ pixel blocks is computed and compared with a cost ofpartitioning the LCU portion into a ‘16×16’ pixel block configured bythe four ‘4×4’ pixel blocks collectively. In an embodiment, the cost ofpartitioning the LCU portion into four ‘4×4’ pixel blocks is computed bysumming individual RDO costs associated with principal intra-predictionmodes for each of the four ‘4×4’ pixel blocks and a cost of encodingfour intra-prediction modes associated with the four ‘4×4’ pixel blocks.Similarly, the cost of partitioning the LCU portion into a ‘16×16’ pixelblock is computed by summing a RDO cost associated with principalintra-prediction mode of the ‘16×16’ pixel block and a cost of encodinga single principal intra-prediction mode. The costs of partitioning theLCU portion in both cases are compared, for example by using thecomparison module 208, and a PU size for partitioning the LCU portion isdetermined by the decision module 210 based on least cost criterion.

As explained above, the determination of intra-prediction mode for eachpixel block is computationally intensive and needs to be reduced forefficiency purposes. It is noted that though the reduction inintra-prediction estimation computation is explained herein withreference to ‘64×64’ pixel block size, the computation logic isapplicable to other pixel block sizes, such as ‘8×8’, ‘16×16’ and‘32×32’ as well with requisite adjustments, such as disabling highertransform computations etc. Further, the reduction in intra-predictionestimation computation is explained with reference to the video codingstandard HEVC. However, it is noted that embodiments as described hereinare not limited to HEVC. In HEVC, the LCU is the base unit used forblock-based coding. A picture is divided into non-overlapping LCUs. Thatis, an LCU plays a similar role in coding as the macro block ofH.264/AVC, but it may be larger, e.g., 32×32, 64×64, etc. An LCU may bepartitioned into coding units (CU). A CU is a block of pixels within anLCU and the CUs within an LCU may be of different sizes. Thepartitioning is a recursive quadtree partitioning. The quadtree is splitaccording to various criteria until a leaf is reached, which is referredto as the coding node or coding unit. The maximum hierarchical depth ofthe quadtree is determined by the size of the smallest CU (SCU)permitted. The coding node is the root node of two trees, a predictiontree and a transform tree. A prediction tree specifies the position andsize of prediction units (PU) for a coding unit. A transform treespecifies the position and size of transform units (TU) for a codingunit. A transform unit may not be larger than a coding unit and the sizeof a transform unit may be 4×4, 8×8, 16×16, and 32×32. The sizes of thetransforms units and prediction units for a CU are determined by a videoencoder during prediction based on minimization of rate/distortioncosts. For simplicity of explanation, a 4:2:0 sampling rate is assumedin which for each 2×2 luma sample, there are two corresponding chromasamples. It is noted herein that luma and chroma blocks in a block ofvideo data may be derived differently for intra-prediction.

In an embodiment, the IPE device 204 is configured to access four ‘N×N’pixel blocks from the memory device 202. The four ‘N×N’ pixel blockscollectively configure a ‘2N×2N’ pixel block of a video picture. In anembodiment, the four ‘N×N’ pixel blocks include luma related pixels. Thepixel blocks including such luma specific information are hereinafterreferred as luma blocks. In an embodiment, ‘N’ is an integer value fromamong one of 8, 16 and 32. The intra-prediction estimation as explainedhereinafter is performed using a value of ‘N’ to be 32. Accordingly, theIPE device 204 accesses four ‘32×32’ luma blocks configuring a ‘64×64’luma block of a video picture. However, it is noted that though theexplanation for intra-prediction estimation for value of ‘N’ as 32 isapplicable to values of ‘N’ as 8 or 16, requisite adjustments may needto be performed for ensuring applicability, such as disabling highertransform computations etc. Further, it is noted that intra-predictionestimation as explained herein assumes that prediction is performed attransform boundaries.

In an embodiment, the IPE device 204 is configured to access a firstpre-determined number of candidate luma intra-prediction modes(hereinafter referred to as luma modes) for each of the four ‘32×32’pixel blocks by the IPE device 204. In an embodiment, a candidacy of aluma mode is determined based on a pre-defined measure. In anembodiment, the predefined measure is one of SAD cost and SATD cost. Itis noted that the term ‘candidate’ intra-prediction modes (for both lumaand chroma components) as used herein refers to those intra-predictionmodes, which are most likely to be selected as a principalintra-prediction mode for a given pixel block. For example, if lumamodes—3, 5 and 7—are accessed as candidate luma modes for a ‘32×32’ lumablock, then the principal luma mode for the ‘32×32’ luma block is mostlikely to be one of 3, 5 and 7.

As explained with reference to FIG. 1, SAD (or SATD) cost computation isperformed for each of the suggested 35 luma modes and a small set (e.g.pre-determined number) of candidate luma modes are selected from amongthe 35 luma modes based on minimization of SAD/SATD cost. In anembodiment, the cost computation module 206 is configured to performSAD/SATD cost computation for the 35 luma modes for each ‘32×32’ lumablock. The comparison module 208 compares the SAD/SATD costs for the 35luma modes and identifies a pre-determined number, for example three,luma modes from among the 35 luma modes for each of the four ‘32×32’pixel blocks based on least SAD costs. The identified three luma modesbased on least SAD/SATD costs for each of the four ‘32×32’ luma blocksare termed as the candidate luma modes for the corresponding ‘32×32’luma blocks. The cost computation module 206 is further configured toperform RDO cost computation for the three luma modes for each ‘32×32’luma block and identify the principal luma mode for each ‘32×32’ lumablock.

In an embodiment, the pre-determined number of candidate luma modes for‘32×32’ luma blocks are stored in the memory device 202 and are reusedfor determining the principal luma mode for ‘64×64’ luma block. In anembodiment, the IPE device 204 receives the stored pre-determined numberof candidate luma modes for each of the four ‘32×32’ luma blocks.

In an embodiment, the IPE device 204 is configured to identify apresence of one or more luma modes that are common among the candidateluma modes of at least two of the four ‘32×32’ pixel blocks. Morespecifically, the comparison module 208 of the IPE device 204 comparesthe candidate luma modes for the four ‘32×32’ luma blocks and identifiesone or more luma modes that are common to at least two of those four‘32×32’ luma blocks.

In an embodiment, the IPE device 204 is configured to select a principalluma mode for the ‘64×64’ luma block from among the one or more lumamodes upon identifying the presence of the one or more luma modes thatare common among the candidate luma modes of at least two of the four‘32×32’ pixel blocks. In an embodiment, the IPE device 204 is configuredto perform limiting a partitioning size to ‘32×32’ luma block size for aportion of the video picture corresponding to the ‘64×64’ luma blockupon determining an absence of the one or more luma modes that arecommon to at least two of the four ‘32×32’ pixel blocks. Morespecifically, if the comparison module 208 of the IPE device 204determines that there are no common luma modes from among the candidateluma modes for the four ‘32×32’ luma blocks, then the decision module210 limits a LCU partitioning size to ‘32×32’ luma block size for aportion of the video picture corresponding to the ‘64×64’ luma block,thereby precluding the need to identify the principal luma mode for the‘64×64’ luma block and also the need to compute a cost of partitioningthe luma block region into ‘64×64’ luma block or into four ‘32×32’ lumablocks.

In an embodiment, if a presence of a luma mode from among the one ormore luma modes that is common to each of the four ‘N×N’ luma blocks isdetermined, then the luma mode is selected as the principal luma modefor the ‘2N×2N’ luma block. For example, during the intra-predictionestimation for ‘64×64’ luma block, the stored candidate luma modes forfour ‘32×32’ luma blocks (which configure the ‘64×64’ luma block) areaccessed and compared by the comparison module 208 to identify if anyluma mode is common among the candidate luma modes for the four ‘32×32’luma blocks. If the comparison module 208 determines that there is aluma mode that is common to all of the four ‘32×32’ luma blocks, thenthat luma mode is selected as the principal luma mode for the ‘64×64’luma block. As a result of re-using the candidate luma modes from four‘32×32’ luma blocks for intra-prediction estimation of ‘64×64’ lumablock, a SAD/SATD computation for 35 luma modes as well as RDOcomputation for candidate luma modes for identifying the principal lumamode for the ‘64×64’ luma block can be skipped altogether, therebyenabling sizable saving in computational complexity.

In an embodiment if a presence of two or more luma modes that are commonto each of the four ‘N×N’ pixel blocks is identified, then a luma modeis selected from among the two or more luma modes as the principal lumamode for the ‘2N×2N’ pixel block based on RDO cost associated with eachof the two or more luma modes. For example, if two intra-predictionmodes—mode 5 and mode 11—are common among the three candidate luma modesfor each of the four ‘32×32’ luma blocks, then a RDO cost for modes 5and 11 stored in the memory device 202 is retrieved, added for the four‘32×32’ luma blocks and compared to determine one luma mode from amongmodes 5 and 11 as the principal luma mode for the ‘64×64’ luma block.Again, as a result of re-using the candidate luma modes and thecorresponding RDO costs from four ‘32×32’ luma blocks forintra-prediction estimation of ‘64×64’ luma block, a SAD/SATDcomputation for 35 luma modes as well as RDO computation for candidateluma modes for identifying the principal luma mode for the ‘64×64’ lumablock can be skipped altogether, thereby enabling sizable saving incomputational complexity.

In an embodiment, if the presence of the one or more luma modes that arecommon to two or three ‘N×N’ luma blocks from among the four ‘N×N’ lumablocks is determined by the IPE device 204, then the IPE device 204 isconfigured to associate the one or more luma modes with the remainingluma blocks from among the four ‘N×N’ luma blocks. For example, if twoluma modes—mode 9 and mode 12—are common to only two of the four ‘32×32’luma blocks, then the modes 9 and 12 are associated with the remainingtwo of the four ‘32×32’ luma blocks.

In an embodiment, the IPE device 204 is further configured to computeRDO cost for each of one or more luma modes for the remaining lumablocks, and, select a luma mode from among the one or more luma modes asthe principal luma mode for the ‘2N×2N’ luma block based on the RDO costassociated with each of the one or more luma modes. For example, uponassociating luma modes 9 and 12 with the remaining luma blocks of thefour ‘32×32’ luma blocks (such that all four of the ‘32×32’ luma blockhave 9 and 12 as the candidate luma mode), an RDO cost of 9 and 12 iscomputed for remaining ‘32×32’ luma blocks and a luma mode with theleast RDO cost from among 9 and 12 is chosen as the principal luma modefor the ‘64×64’ luma block. As a result of re-using the candidate lumamodes and the corresponding RDO costs from four ‘32×32’ luma blocks forintra-prediction estimation of ‘64×64’ luma block, a SAD/SATDcomputation for 35 luma modes as well as RDO computation for candidateluma modes for identifying the principal luma mode for the ‘64×64’ lumablock can be reduced sizably (as only ˜1 to 2 RDO computations needs tobe performed), thereby enabling sizable saving in computationalcomplexity. The selection of the principal luma intra-prediction mode isfurther explained with reference to FIG. 3.

FIG. 3 depicts an exemplary visual representation of four ‘32×32’ lumablocks for illustrating selection of a principal luma mode for a ‘64×64’luma block in accordance with an embodiment. As explained with referenceto FIG. 2, the IPE device 204 accesses four ‘32×32’ luma blocks alongwith a pre-determined number of candidate luma modes for each of thefour ‘32×32’ luma blocks. One or more luma modes from among thecandidate luma modes that are common to at least two of the four ‘32×32’blocks is identified and a principal luma mode selected from among theone or more luma modes. In FIG. 3, four ‘32×32’ luma blocks, such asblock 302, block 304, block 306 and block 308, which collectivelyconfigure a ‘64×64’ luma block such as block 310, are accessed by theIPE device 204. Further, as explained with reference to FIG. 2, thecandidate luma modes (based on SAD/SATD computation), associated RDOcosts and reconstruction data for principal luma mode corresponding tothe four ‘32×32’ luma blocks 302-308, which were determined duringintra-prediction estimation of each of the four ‘32×32’ luma blocks302-308 are stored in the memory device 202. During the intra-predictionestimation of block 310, the candidate luma modes for the four ‘32×32’luma blocks 302-308 are accessed from the memory device 202. Theaccessed candidate luma modes for blocks 302-308 are (0, 1, 5), (1, 5,7), (0, 1, 5) and (0, 1, 8) respectively. In FIG. 3, the pre-determinednumber of candidate luma modes for each of the four ‘32×32’ luma blocksis chosen to be three, however, it is noted that the pre-determinednumber of candidate luma modes may be greater or lesser than three. Theprincipal luma modes based on RDO computation for the ‘32×32’ lumablocks 302-308 are 1, 5, 5 and 8 respectively (depicted by underlinednumerals in FIG. 3).

The comparison module 208 of FIG. 2 is configured to compare theaccessed candidate luma modes and determine a presence of one or moreluma modes that are common to at least two of the four ‘32×32’ lumablocks. In FIG. 3, it is determined that luma mode ‘1’ is common to allfour of ‘32×32’ luma blocks. Accordingly, luma mode ‘1’ is selected asthe principal luma mode for the ‘64×64’ luma block 310. Estimation ofthe intra-prediction mode for ‘64×64’ luma block in such a manner (e.g.by reusing candidate luma modes of ‘32×32’ luma blocks) precludes theneed to perform SAD and RDO computations for determining the principalluma mode for the ‘64×64’ luma block, thereby leading to sizableresource and power saving.

In an embodiment, if it was determined that two or more of the threecandidate luma modes are common to all four blocks 302-308, then a RDOcost associated with each of two or more luma modes are accessed fromthe memory device 202 and compared by the comparison module 208. Theluma mode associated with the least RDO cost is selected as theprincipal luma mode for ‘64×64’ luma block 310. For example, if lumamodes 10 and 12 (not shown in FIG. 3) are common to all four luma blocks302-308, then a RDO costs for luma modes 10 and 12 are accessed andcompared with each other. The luma mode with the least RDO cost isselected as the principal luma mode for block 310. It is noted that theRDO cost for luma mode 10 may be computed by summing a RDO cost for mode10 for each of the blocks 302-308. Similarly, the RDO cost for luma mode12 may be computed by summing a RDO cost for mode 12 for each of theblocks 302-308.

As explained with reference to FIG. 2, if it is determined that one ofmore luma modes are common to two or three luma blocks from among theluma blocks 302-308, then the one or more luma modes are associated withthe remaining luma blocks and a luma mode selected from among the one ormore luma modes based on least RDO cost. For example, if luma modes 2and 3 (not shown in FIG. 3) are common to blocks 302 and 304 only, thenthe luma modes 2 and 3 may be associated with the remaining luma blocks,e.g. blocks 306 and 308. A RDO cost for the luma modes 2 and 3 iscomputed for remaining blocks 306 and 308, such that RDO cost for lumamodes 2 and 3 is now available for all four blocks 302-308. A RDO costfor luma modes 2 and 3 is then summed for all four blocks, respectively,and compared with each other. A principal luma mode is then selectedfrom among luma modes 2 and 3 based on least RDO cost. It is notedherein that though determination of the principal luma mode involvessome RDO computations, a number of RDO computations is drasticallyreduced as compared to conventional techniques of determining theprincipal luma mode by performing RDO computation for each of 35 lumaintra-prediction modes.

In an embodiment, if it was determined that none of the luma modes fromamong the three candidate luma modes for blocks 302-308 are common, thenthe decision module 210 of FIG. 2 determines that computation of theprincipal luma mode for block 310 be avoided altogether and the block310 be partitioned into PU size of ‘32×32’ e.g. into blocks 302-308.

In an embodiment, upon determining the principal luma mode for block310, a first partitioning cost associated with the block 310 (e.g. a‘64×64’ luma block) is computed based on the selected principal lumamode, e.g. mode ‘1’. Further, a second partitioning cost associated thefour ‘32×32’ luma blocks is computed and compared with the firstpartitioning cost. A partitioning size for a portion of the videopicture corresponding to the ‘64×64’ luma block is determined based onthe comparison between the first partitioning cost and the secondpartitioning cost. More specifically, the partitioning size is chosenbased on least partitioning cost from among the first partitioning costand the second partitioning cost. As explained above, the principal lumamodes for blocks 302-308 are 1, 5, 5 and 8 respectively. A RDO costassociated with each of these principal luma modes are obtained andsummed with the cost of encoding/transmitting the luma modes (e.g. costof transmitting modes 1, 5 and 8) to configure the second partitioningcost, e.g. the cost of partitioning the LCU in ‘32×32’ PU size.Similarly, the RDO cost associated with principal luma mode ‘1’ forblock 310 is added to the cost of encoding/transmitting luma mode ‘1’ toconfigure the first partitioning cost, e.g. the cost of partitioning theLCU in ‘64×64’ PU size. Upon comparison of the first partitioning costand the second partitioning cost, a partitioning size is chosen fromamong the two based on least cost.

In an embodiment, a pixel block adjacent (for example, right neighboringpixel block) to the ‘2N×2N’ pixel block is configured to receiveadjusted reconstructed data for performing luma intra-predictionestimation if it is determined that the first partitioning cost is lessthan the second partitioning cost, implying selecting a partitioningsize for ‘2N×2N’ pixel block to be ‘2N×2N’. The provisioning of thereconstructed data is explained as follows: As explained above, the IPEdevice 204 is configured to store reconstruction data corresponding tothe principal luma mode in the memory device 202. In an embodiment, thereconstruction data corresponds to boundary pixel values that can beused by the adjacent luma block for intra-prediction estimationpurposes. Accordingly, in FIG. 3, during intra-prediction estimation offour ‘32×32’ luma blocks 302-308, the reconstruction data correspondingto principal luma modes 1, 5, 5 and 8 are stored in the memory device202. It is noted that in some embodiments, reconstruction datacorresponding to candidate luma modes (in addition to the principal lumamode) may be stored in the memory device 202. A subsequentintra-prediction estimation of ‘64×64’ luma block 310 (configured of thefour ‘32×32’ luma blocks) may result in determination of mode “1” as theprincipal luma mode and a partitioning cost computation may result inthe first partitioning cost being less than the second partitioning costimplying selection of luma block 310 as the PU block for the LCU.However, the reconstruction data for mode “1” may not available forportions of the block 310 corresponding to blocks 304 and 308 (asreconstruction data corresponding to luma modes 5 and 8 is stored forthese blocks and the intra-prediction estimation for block 310 may skipRDO computation for mode ‘1’). Accordingly, if it is determined that theLCU size is ‘64×64’ than the reconstruction data used forintra-prediction estimation for an adjacent right block corresponds tomodes ‘5’ and ‘8’ (i.e. adjusted reconstructed data) as opposed toprincipal luma mode ‘1’ of ‘64×64’ pixel block. On account of performingintra-prediction estimation for ‘64×64’ luma block as explained withreference to FIGS. 2 and 3, left boundary reconstruction data for nextadjoining block may or may not correspond to that of the principal lumamode if the LCU is a ‘64×64’ luma block. Instead, stored values ofprincipal luma modes for ‘32×32’ luma blocks are used forintra-prediction estimation. Or in other words, if it is determined thatthe LCU size is ‘64×64’, then the right neighboring block may receivethe principal luma mode of the left neighboring block, which may or maynot be the principal luma mode of ‘64×64’ luma block and hence referredherein as adjusted reconstructed data. It is noted that that suchutilization of adjusted reconstructed data does not have any sizableaffect on a quality of intra-prediction.

In an embodiment, a determination of principal chroma mode is similarlyperformed as explained with reference to FIGS. 2 and 3. Thedetermination of the principal chroma mode is further explained below.

Referring now to FIG. 2, the IPE device 204 is also configured to accessfour pixel blocks including chroma related pixels from the memory device202. The four pixel blocks collectively configure a chroma pixel block(hereinafter referred to as chroma block) corresponding to the ‘2N×2N’pixel block. The chroma intra-prediction estimation as explained hereinassumes an exemplary downsampling scheme of 4:2:0 adopted by the system200. However, it is noted that any such downsampling scheme may beadopted by the system 200 and the downsampling scheme of 4:2:0 may notbe considered limiting. Accordingly, a ‘2N×2N’ luma block is associatedwith two corresponding chroma blocks (for example, C_(b) and C_(r)) ofsize ‘N×N’. It is noted that the determination of principal chroma modeis explained herein with reference to one chroma component (either C_(b)or C_(r)) and that such determination is applicable to the other chromacomponent. In an embodiment, the IPE device 204 accesses four ‘N/2×N/2’chroma blocks configuring an ‘N×N’ chroma block corresponding to the‘2N×2N’ luma block of the video picture. For example, the IPE device 204accesses four ‘16×16’ chroma blocks configuring a ‘32×32’ chroma blockcorresponding to a ‘64×64’ luma block. It is noted that theintra-prediction estimation for chroma component is explained hereinwith reference to ‘32×32’ chroma block, e.g. four ‘16×16’ chroma blocks.However, different configurations of chroma blocks may be contemplatedfor chroma intra-prediction estimation with requisite adjustments (e.g.disabling of higher transforms etc.).

The IPE device 204 is further configured to access a secondpre-determined number of candidate chroma inter-prediction modes(hereinafter referred to as chroma modes) for each of the four ‘N/2×N/2’chroma blocks. In an embodiment, a candidacy of the chroma modes isdetermined based on a predefined measure. In an embodiment, thepredefined measure is one a SAD cost and SATD cost. Video codingstandards, such as HEVC suggest 5 intra-prediction modes for chromaintra-prediction purposes. Accordingly, the second pre-determined numberof candidate chroma modes may be any number from 1 to 5. For example, inan embodiment, the pre-determined number of candidate chroma modes ischosen as three. Accordingly, the cost computation module 206 computesSAD/SATD costs for five chroma modes during intra-prediction estimationof each ‘16×16’ chroma block. The comparison module 208 compares theSAD/SATD costs for the five chroma modes and determines a secondpre-determined number (for example, three) candidate chroma modes fromamong the five chroma modes for each of the four ‘16×16’ chroma blocks.

In an embodiment, the IPE device 204 is configured to identify apresence of one or more chroma modes that are common from among thecandidate chroma intra-prediction modes of at least two of the four‘N/2×N/2’ pixel blocks. More specifically, the comparison module 208compares the candidate chroma modes of the four ‘16×16’ chroma blocksand determines if any chroma mode is common to at least two of the four‘16×16’ chroma blocks.

In an embodiment, a presence of the principal luma mode for ‘2N×2N’ lumablock in the one or more chroma modes is identified by the IPE device204 subsequent to identifying the presence of one or more chroma modesthat are common among the candidate chroma modes. In an embodiment, thepresence of principal luma mode is determined upon identifying thepresence of one or more chroma modes to be present from among thecandidate chroma modes. For example, if the principal luma mode for the‘64×64’ luma block is ‘1’, then a presence of mode ‘1’ is checked withinthe one or more chroma modes that are common among the candidate chromaintra-prediction modes of at least two of the four ‘16×16’ chromablocks.

In an embodiment, if the principal luma mode for ‘2N×2N’ luma block isdetermined to be present from among the one or more chroma modes, thenthe IPE device 204 is configured to select the principal chroma modefrom among the one or more chroma intra-prediction modes based on RDOcost associated with each of the candidate chroma intra-predictionmodes. In an embodiment, if the principal luma mode for the ‘2N×2N’ lumablock is determined to be absent from among the one or more chromamodes, then the IPE device 204 is configured to associate the principalluma mode with each of the four ‘N/2×N/2’ chroma blocks. The IPE device204 is further configured to select the principal chroma mode from amongthe one or more chroma modes and the principal luma mode based on RDOcost associated with each of the one or more chroma modes and theprincipal luma mode. In an embodiment, a pixel block adjacent to thechroma pixel block is configured to receive adjusted reconstructed datafor performing chroma intra-prediction estimation a pixel block sizecorresponding to the chroma pixel block is chosen as the partitioningsize for a portion of the video picture corresponding to the chromapixel block. The provisioning of the reconstructed data is performed asexplained in conjunction with luma blocks and is not explained hereinfor sake of brevity. The selection of the principal chroma mode isfurther explained with reference to FIG. 4.

FIG. 4 depicts an exemplary visual representation of four ‘16×16’ chromablocks for illustrating selection of the principal chroma mode for a‘32×32’ chroma block in accordance with an embodiment. Video codingstandards, such as the HEVC suggest five chroma intra-prediction modesfor performing chroma intra-prediction.

As explained with reference to FIG. 2, the IPE device 204 receives four‘16×16’ chroma blocks along with a pre-determined number of candidatechroma modes for each of the four ‘16×16’ chroma blocks. A presence ofone or more chroma modes that are common among the candidate chromamodes of at least two of the four ‘16×16’ chroma blocks is identified. Apresence of the principal luma mode for ‘64×64’ luma block (thatcorresponds to the ‘32×32’ chroma block configured by the four ‘16×16’chroma blocks) is determined in the one or more chroma modes and theprincipal luma mode is considered during RDO computation for determiningthe principal chroma mode.

In FIG. 4, four ‘32×32’ luma blocks 404, 406, 408 and 410 whichconfigure a ‘64×64’ luma block 402 are depicted. During the processingof luma blocks of PU size ‘32×32’, a determination of principal lumamodes may already be performed for blocks 404-410. In FIG. 4, theprincipal luma modes for blocks 404-410 are 11, 5, 5 and 8 (depicted byunderlined numerals). This information is stored in the memory device202. The principal luma mode for ‘64×64’ luma block is determined to be11 as explained with reference to FIGS. 2 and 3 and this information isalso stored in the memory device 202.

FIG. 4 also depicts four ‘16×16’ chroma blocks 414, 416, 418 and 420configuring a ‘32×32’ chroma block 412 corresponding to the ‘64×64’ lumablock 402. It is noted herein that eight ‘16×16’ chroma blocks(corresponding to chroma C_(b) and C_(r) components) may be determinedcorresponding to the ‘64×64’ luma block 402, however, chromaintra-prediction is explained herein with reference to only any one ofthe chroma components (e.g. four ‘16×16’ chroma blocks). Each of fourchroma blocks is associated with five chroma intra-prediction modes.Four of those modes correspond to DC, Vertical, Horizontal and Planarmodes, which are 0, 1, 2 and 3 as depicted in FIG. 4. The fifth chromaintra-prediction mode is the principal luma mode from the correspondingluma block. Accordingly, the principal luma modes from corresponding‘32×32’ luma blocks 404, 406, 408 and 410 (e.g. 11, 5, 5 and 8respectively) are associated with the blocks 414, 416, 418 and 420.Accordingly, the five chroma intra-prediction modes for blocks 414, 416,418 and 420 are (0, 1, 2, 3 and 11), (0, 1, 2, 3 and 5), (0, 1, 2, 3 and5) and (0, 1, 2, 3 and 8) respectively. A RDO cost computation isperformed (for example, by the cost computation module 206 of FIG. 2) todetermine the principal chroma mode for each of the four ‘16×16’ chromablocks during intra-prediction estimation for each of the four ‘16×16’chroma blocks. The principal chroma modes determined for the blocks 414,416, 418 and 420 are 3, 1, 5, and 8 respectively (depicted as underlinednumerals in FIG. 4).

The cost computation module 206 performs a SAD cost computation for eachof the five chroma intra-prediction modes and identifies the top threecandidate chroma modes with the least SAD cost during theintra-prediction estimation for four ‘16×16’ chroma blocks. The topthree candidate chroma modes for each of the four ‘16×16’ chroma blocksare stored in the memory device 202 and later accessed duringintra-prediction estimation of the ‘32×32’ chroma block 412. It is notedthat the pre-defined number three is chosen for illustration purposesand that the pre-defined number may be any number greater or smallerthan three. Further it is noted that the pre-defined measure ofcandidacy, e.g. SAD cost, is mentioned herein for example purposes andany such measure, for example SATD cost and the like, may be utilizedfor identifying the top three candidate chroma modes.

In an embodiment, the comparison module 206 is configured to determineone or more chroma modes from among the candidate chroma modes that arecommon to at least two of the four ‘16×16’ chroma blocks. In anembodiment, a presence of principal luma mode for ‘64×64’ luma blockfrom among the one or more chroma modes (for four ‘16×16’ chroma blocks)is determined. If it is determined that the principal luma mode (forexample ‘1’) is present among the one or more chroma modes, then an RDOcost computation is performed for the one or more chroma modes toidentify the principal chroma mode for the ‘32×32’ chroma block 412. Ifit is determined that the principal luma mode for ‘64×64’ luma block isnot among the one or more chroma modes for the blocks 414, 416, 418 and420, then the principal luma mode is associated with the each of theblocks 414, 416, 418 and 420 and a RDO cost computation is performed forthe one or more chroma modes and principal luma mode to identify theprincipal chroma mode.

As explained, the system 200 may be included with a video processingdevice and may include components for performing various functions,which are not depicted herein. For example, the system 200 mayadditionally include components, such as an input unit (e.g., an imageprocessing device), a video display unit (e.g., liquid crystals display(LCD), a cathode ray tube (CRT), and the like), a cursor control device(e.g., a mouse), a drive unit (e.g., a disk drive), a signal generationunit (e.g., a speaker) and/or a network interface unit. The input unitis configured to transfer the video pictures corresponding to a videodata sequence to the memory device 202 in order to facilitateintra-prediction estimation of video pictures. The drive unit includes amachine-readable medium upon which is stored one or more sets ofinstructions (e.g., software) embodying one or more of the methodologiesand/or functions described herein. In an embodiment, the softwareresides, either completely or partially, within the memory device 202,and/or within the IPE device 204 during the execution thereof by thesystem 200, such that the IPE device 204 and memory device 202 alsoconstitute a machine-readable media. The software may further betransmitted and/or received over a network via the network interfaceunit.

The term “machine-readable medium” may be construed, for example, toinclude a single medium and/or multiple media (e.g., a centralizedand/or distributed database, and/or associated caches and servers) thatstore the one or more sets of instructions. Moreover, the term“machine-readable medium” may be construed, for example, to include anymedium that is capable of storing, encoding and/or carrying a set ofinstructions for execution by the system 200 and that cause the system200 to perform any one or more of the methodologies of the variousembodiments. Furthermore, the term “machine-readable medium” may beconstrued to include, but shall not be limited to, solid-state memories,optical and magnetic media, and carrier wave signals. The foregoingnotwithstanding, it is noted that the present technology is not limitedto any particular definition of “machine-readable medium”. A method forluma intra-prediction estimation is explained with reference to FIGS. 5Aand 5B.

FIGS. 5A and 5B illustrate a flow diagram of an exemplary method 500 ofluma intra-prediction estimation in accordance with an exampleembodiment. The method 500 depicted in the flow diagram may be executedby, for example, the system 200 explained with reference to FIG. 2.Operations of the flowchart, and combinations of operation in theflowchart, may be implemented by, for example, hardware, firmware, aprocessor, circuitry and/or a different device associated with theexecution of software that includes one or more computer programinstructions. The operations of the method 500 are described herein withhelp of the system 200. However, the operations of the method can bedescribed and/or practiced by using a system other than the system 200.The method 500 starts at operation 502.

At operation 502, four ‘N×N’ pixel blocks are accessed by anintra-prediction estimation device, such as the IPE device 204 of FIG.2. The four ‘N×N’ pixel blocks collectively configure a ‘2N×2N’ pixelblock of a video picture. In an embodiment, the four ‘N×N’ pixel blocksinclude luma related pixels. The pixel blocks including such lumaspecific information are referred as luma blocks. In an embodiment, ‘N’is an integer value with value from one among 8, 16 and 32. For example,the intra-prediction estimation device accesses four ‘32×32’ luma blocksconfiguring a ‘64×64’ luma block.

At operation 504, a first pre-determined number of candidate lumaintra-prediction modes (e.g. luma modes) for each of the four ‘N×N’pixel blocks are accessed by the intra-prediction estimation device. Inan embodiment, the candidacy of the luma intra-prediction modes isdetermined based on a predefined measure. In an embodiment, thepredefined measure is one a SAD cost and a SATD cost. As explained withreference to FIGS. 2 and 3, during intra-prediction estimation of each‘N×N’ luma block based on the HEVC standard, a SAD cost is computed foreach of the 35 luma modes and a pre-determined number (for example,three) of candidate luma modes is selected based on the least SAD costs.The pre-determined number of candidate luma modes for each of the four‘N×N’ pixel blocks are stored at a storage location (for example, memorydevice 202 of the system 200). The intra-prediction estimation deviceaccesses the stored pre-determined number of candidate luma modes duringintra-prediction estimation of ‘2N×2N’ luma block.

At operation 506, a presence of one or more luma intra-prediction modesthat are common from among the candidate luma intra-prediction modes ofat least two of the four ‘N×N’ pixel blocks is determined by theintra-prediction estimation device. If it is determined that none of theluma intra-prediction modes are common to at least two of the four ‘N×N’luma blocks then at operation 508, a partitioning size is limited to‘N×N’ pixel block size for a portion of the video picture correspondingto the ‘2N×2N pixel block, thereby precluding the need to identify theprincipal luminance mode for the ‘2N×2N’ luma block and also the need tocompute a cost of partitioning the luma block region into ‘2N×2N’ lumablock or into four ‘N×N’ luma blocks.

Alternatively, if one or more luma modes that are common to at least twoof the four ‘N×N’ pixel blocks is determined to be present, then atoperation 510, it is determined if only one luma intra-prediction modeis common to all four ‘N×N’ pixel blocks. If it determined that only oneluma intra-prediction mode is common to all four ‘N×N’ pixel blocks,then the common luma intra-prediction mode is selected as the principalluma intra-prediction mode for the ‘2N×2N’ pixel block at operation 512.As a result of re-using the candidate luma modes from four ‘N×N’ lumablocks for intra-prediction estimation of ‘2N×2N’ luma block, a SAD/SATDcomputation for 35 luma modes as well as RDO computation for candidatemodes for identifying the principal luma mode for the ‘2N×2N’ luma blockcan be skipped altogether, thereby enabling sizable saving incomputational complexity.

If at operation 510, it is determined that more than one lumaintra-prediction mode are common to all four ‘N×N’ pixel blocks, then atoperation 514, it is determined if two or more luma intra-predictionmodes are common to all four of the ‘N×N’ pixel blocks. If it isdetermined that two or more luma intra-prediction modes are common toall four of the ‘N×N’ pixel blocks, then at operation 516, a lumaintra-prediction mode from among the two or more luma intra-predictionmodes is selected as the principal luma intra-prediction mode for the‘2N×2N’ pixel block based on the RDO cost associated with each of thetwo or more luma intra-prediction modes. For example, if twointra-prediction modes—mode 5 and mode 11—are common among the threecandidate luma modes for each of the four ‘32×32’ luma blocks, then RDOcosts for modes 5 and 11 stored in the memory device 202 are accessed,added for the four ‘32×32’ luma blocks and compared to determine oneluma mode from among mode 5 and 11 as the principal luma mode for the‘64×64’ luma block. Again, as a result of re-using the candidate lumamodes and the corresponding RDO costs from four ‘32×32’ luma blocks forintra-prediction estimation of ‘64×64’ luma block, a SAD/SATDcomputation for 35 luma modes as well as RDO computation for candidatemodes for identifying the principal luma mode for the ‘64×64’ luma blockcan be skipped altogether, thereby enabling sizable saving incomputational complexity.

If at operation 514, it is determined that two or more lumaintra-prediction modes are not common to all four ‘N×N’ pixel blocks,then at operation 518, it is deduced that one or more lumaintra-prediction modes are common to two or three ‘N×N’ pixel blocksfrom among the four ‘N×N’ pixel blocks. Accordingly, at operation 520,one or more luma intra-prediction modes are associated with theremaining pixel blocks from among the four ‘N×N’ pixel blocks. Forexample, if two luma modes—mode 9 and mode 12—are common to only two ofthe four ‘32×32’ luma blocks, then the modes 9 and 12 are associatedwith the remaining two of the four ‘32×32’ luma blocks. At operation522, RDO cost is computed for each of one or more luma intra-predictionmodes for the remaining pixel blocks. At operation 524, a lumaintra-prediction mode from among the one or more luma intra-predictionmodes is selected as the principal luma intra-prediction mode for the‘2N×2N’ pixel block based on the RDO cost associated with each of theone or more luma intra-prediction modes. For example, upon associatingluma modes 9 and 12 with the remaining luma blocks of the four ‘32×32’luma blocks (such that all four of the ‘32×32’ luma block have 9 and 12as the candidate luma mode), an RDO cost of 9 and 12 is computed for allfour ‘32×32’ luma blocks and a luma mode with the least RDO cost fromamong 9 and 12 is chosen as the principal luma mode for the ‘64×64’ lumablock. As a result of re-using the candidate luma modes and thecorresponding RDO costs from four ‘32×32’ luma blocks forintra-prediction estimation of ‘64×64’ luma block, a SAD/SATDcomputation for 35 luma modes as well as RDO computation for candidatemodes for identifying the principal luma mode for the ‘64×64’ luma blockcan be reduced sizably (as only ˜1 to 2 RDO computations needs to beperformed), thereby enabling sizable saving in computational complexity.A method of chroma intra-prediction estimation is explained withreference to FIGS. 6A and 6B.

FIGS. 6A and 6B illustrate a flow diagram of an exemplary method 600 forchroma intra-prediction estimation in accordance with an embodiment. Themethod 600 depicted in the flow diagram may be executed by, for example,the system 200 explained with reference to FIG. 2. Operations of theflowchart, and combinations of operation in the flowchart, may beimplemented by, for example, hardware, firmware, a processor, circuitryand/or a different device associated with the execution of software thatincludes one or more computer program instructions. The operations ofthe method 600 are described herein with help of the system 200.However, the operations of the method can be described and/or practicedby using a system other than the system 200. The method 600 starts atoperation 602.

At operation 602, four pixel blocks including chroma related pixels areaccessed by an intra-prediction estimation device, such as the IPEdevice 204 of FIG. 2. The four pixel blocks collectively configure achroma pixel block (hereinafter referred to as chroma block)corresponding to the ‘2N×2N’ pixel block. For example, theintra-prediction estimation device acceses four ‘16×16’ chroma blocksconfiguring a ‘32×32’ chroma block corresponding to a ‘64×64’ lumablock. It is noted that the method 600 is explained herein withreference to one chroma component (either C_(b) or C_(r)) however, themethod 600 is applicable to other chroma component as well.

At operation 604, a second pre-determined number of candidate chromaintra-prediction modes (e.g. chroma modes) for each of the four pixelblocks are accessed by the intra-prediction estimation device. In anembodiment, the candidacy of the chroma intra-prediction modes isdetermined based on a predefined measure. In an embodiment, thepredefined measure is one a SAD cost and a SATD cost. As explained withreference to FIGS. 2 and 3, during intra-prediction estimation of eachchroma block based on the HEVC standard, a SAD cost is computed for eachof the five chroma modes and a pre-determined number (for example,three) of candidate chroma modes is selected based on the least SADcosts. The pre-determined number of candidate chroma modes for each ofthe four pixel blocks are stored at a storage location (for example,memory device 202 of the system 200). The intra-prediction estimationdevice accesses the stored second pre-determined number of candidatechroma modes during intra-prediction estimation of ‘N×N’ chroma block.

At operation 606, a presence of one or more chroma intra-predictionmodes that are common from among the candidate chroma intra-predictionmodes of at least two of the four pixel blocks is determined by theintra-prediction estimation device. If it is determined that none of thechroma intra-prediction modes are common to at least two of the fourchroma blocks then at operation 608, a partitioning size is limited to apixel block size corresponding to a pixel block from among the fourpixel blocks for a portion of the video picture corresponding to thechroma pixel block, thereby precluding the need to identify theprincipal chroma mode for the ‘N×N’ chroma block and also the need tocompute a cost of partitioning the chroma block region into ‘N×N’ chromablock or into four ‘N/2×N/2’ chroma blocks.

If it is determined at operation 606 that one or more chroma modes arecommon to at least two of the four chroma blocks, then operation 610 isperformed. At operation 610, it is determined whether a principal lumaintra-prediction mode (e.g. luma mode) for the ‘2N×2N’ luma block(corresponding to the chroma pixel block) is present among the one ormore chroma modes. If it is determined that the principal luma mode ispresent among the one or more chroma modes, then at operation 612, aprincipal chroma intra-prediction mode is selected from among the one ormore chroma modes based on RDO cost associated with each of the one ormore chroma modes.

If it determined at operation 610 that the principal luma mode is notpresent among the one or more chroma modes, then operation 614 isperformed. At operation 614, the principal luma mode is associated witheach of the four pixel blocks. At operation 616, the principal chromaintra-prediction mode is selected from among the one or more chromamodes and the principal luma mode based on RDO cost associated with eachof the one or more chroma intra-prediction modes and the principal lumamode. An integrated circuit configured to facilitate intra-predictionestimation is explained with reference to FIG. 7.

FIG. 7 is a block diagram of an exemplary integrated circuit 702configured to facilitate video picture intra-prediction estimation inaccordance with an embodiment. In an embodiment, the system 200 of FIG.2 is embodied at least partially in the form of the integrated circuit702. The integrated circuit 702 includes a transceiver module 704, acoding module 706, a memory module 708 and a display module 710. Thetransceiver module 704, the coding module 706, the memory module 708 andthe display module 710 are communicatively associated or coupled witheach other using data path 712. As such, it is noted that at least someof the components described below in connection with the integratedcircuit 702 may be optional, and, thus, in an example embodiment theintegrated circuit 702 includes more, less or different components thanthose described in connection with the example embodiment of FIG. 7. Inan embodiment, the integrated circuit 702 may include only the codingmodule 706 and the memory module 708.

The transceiver module 704 is communicatively associated or coupled witha plurality of multimedia resources 714 and is configured to receivevideo pictures from one or more multimedia resources from among theplurality of multimedia resources 714. Examples of the multimediaresources include, but are not limited to (1) remote multimedia systems(2) media capture devices, such as, for example, a camera, camcordersand the like, and (3) multimedia storage devices, such as, for example,magnetic tapes, disks, computer-readable media, and the like. In anembodiment, the transceiver module 704 may include an antenna and/ornetwork connectors configured to couple with or connect to wirednetworks (for example, local area networks (LANs)) and wireless networks(for example, cellular networks), or a combination thereof (for example,the Internet). Examples of network connectors may include a universalserial bus (USB) interface, a wireless LAN interface, an infraredinterface, an Ethernet port, and the like.

The memory module 708 is configured to store the one or more videopictures. In an embodiment, the memory module 708 is substantiallysimilar to the memory device 202 of system 200 of FIG. 2. The memory 708is configured to perform functions as discussed in FIG. 2 with referenceto memory device 202, which are not repeated herein for the sake ofbrevity. Examples of memory module 708 include, but are not limited to,RAM, dual port RAM, SDRAM, DDR SDRAM, and the like.

The coding module 706 is configured to perform at least one ofencoding/decoding of video pictures using the intra-predictionestimation provided by the intra-prediction estimation module 718included therein. In an embodiment, the coding module 706 is configuredto perform one of encoding and decoding of video pictures and providethe encoded/decoded data to the transceiver module 704 for transmissionpurposes or to memory module 708 for storage purposes. In an embodiment,the intra-prediction estimation module 718 is substantially similar tothe IPE device 204 of system 200 of FIG. 2. The intra-predictionestimation module 718 is configured to perform functions as discussed inFIG. 2, which are not repeated herein for the sake of brevity.

The display module 710 is configured to facilitate a display the one ormore video pictures on display 716. The display 716 is facilitated, forexample, in response to a user input received using a user interface(not shown in FIG. 7). Examples of display 716 include a liquid crystaldisplay (LCD) panel, a plasma display panel, a field emission displayand the like.

In an embodiment the integrated circuit 702 is an application processorchip. In an embodiment, the integrated circuit 702 is a part of aparticular or shared processor chip that is embedded within a multimediasystem. Examples of the multimedia system include, but are not limitedto, (1) multimedia devices, such as, for example, cellular phones,digital video cameras and digital camcorders; (2) data processingdevices, such as, for example, personal computers, laptops and personaldigital assistants; and (3) consumer electronics, such as, for example,set top boxes, digital video disk (DVD) players and video networkservers.

Without in any way limiting the scope, interpretation, or application ofthe claims appearing below, advantages of one or more of the exampleembodiments disclosed herein include facilitating intra-predictionestimation of video pictures with reduced computational complexity.Methods and systems disclosed herein suggest re-using of the candidateluma modes and associated RDO costs from four ‘N×N’ luma blocks forintra-prediction estimation of ‘2N×2N’ luma block. Accordingly, aSAD/SATD computation for 35 luma modes as well as RDO computation forcandidate modes for identifying the principal luma mode for the ‘2N×2N’luma block can be skipped altogether, thereby enabling sizable saving incomputational complexity. In some scenarios wherein candidate luma modesare common among only two or three luma blocks, a SAD/SATD computationfor 35 luma modes as well as RDO computation for candidate modes foridentifying the principal luma mode for the ‘64×64’ luma block can bereduced sizably (as only ˜1 to 2 RDO computations need to be performed),thereby enabling sizable saving in computational complexity. TheSAD/SATD costs as well as RDO cost for ‘N/2×N/2’ chroma blocks may bereused for chroma intra-prediction estimation of ‘N×N’ chroma block aswell with minor additional RDO computation for 8 ‘N/2×N/2’ chroma blocks(e.g. four each for each chroma component C_(b) and C_(r)) thus reducingthe number of computations required for determining the principal chromaintra-prediction mode.

Although the present technology has been described with reference tospecific example embodiments, it is noted that various modifications andchanges may be made to these embodiments without departing from thebroad spirit and scope of the present technology. For example, thevarious devices, modules, analyzers, generators, etc., described hereinmay be enabled and operated using hardware circuitry (for example,complementary metal oxide semiconductor (CMOS) based logic circuitry),firmware, software and/or any combination of hardware, firmware, and/orsoftware (for example, embodied in a machine-readable medium). Forexample, the various electrical structures and methods may be embodiedusing transistors, logic gates, and electrical circuits (for example,application specific integrated circuit (ASIC) circuitry and/or inDigital Signal Processor (DSP) circuitry).

Particularly, the system 200, the IPE device 204 and the memory device202 may be enabled using software and/or using transistors, logic gates,and electrical circuits (for example, integrated circuit circuitry suchas ASIC circuitry). Various embodiments of the present disclosure mayinclude one or more computer programs stored or otherwise embodied on acomputer-readable medium, wherein the computer programs are configuredto cause a processor or computer to perform one or more operations. Acomputer-readable medium storing, embodying, or encoded with a computerprogram, or similar language, may be embodied as a tangible data storagedevice storing one or more software programs that are configured tocause a processor or computer to perform one or more operations. Suchoperations may be, for example, any of the steps or operations describedherein. In some embodiments, the computer programs may be stored andprovided to a computer using any type of non-transitory computerreadable media. Non-transitory computer readable media include any typeof tangible storage media. Examples of non-transitory computer readablemedia include magnetic storage media (such as floppy disks, magnetictapes, hard disk drives, etc.), optical magnetic storage media (e.g.magneto-optical disks), CD-ROM (compact disc read only memory), CD-R(compact disc recordable), CD-R/W (compact disc rewritable), DVD(Digital Versatile Disc), BD (Blu-ray (registered trademark) Disc), andsemiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM(erasable PROM), flash ROM, RAM (random access memory), etc.).Additionally, a tangible data storage device may be embodied as one ormore volatile memory devices, one or more non-volatile memory devices,and/or a combination of one or more volatile memory devices andnon-volatile memory devices. In some embodiments, the computer programsmay be provided to a computer using any type of transitory computerreadable media. Examples of transitory computer readable media includeelectric signals, optical signals, and electromagnetic waves. Transitorycomputer readable media can provide the program to a computer via awired communication line (e.g. electric wires, and optical fibers) or awireless communication line.

Also, techniques, devices, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present technology.Other items shown or discussed as directly coupled or communicating witheach other may be coupled through some interface or device, such thatthe items may no longer be considered directly coupled with each otherbut may still be indirectly coupled and in communication, whetherelectrically, mechanically, or otherwise, with one another. Otherexamples of changes, substitutions, and alterations ascertainable by oneskilled in the art, upon or subsequent to studying the exampleembodiments disclosed herein, may be made without departing from thespirit and scope of the present technology.

It should be noted that reference throughout this specification tofeatures, advantages, or similar language does not imply that all of thefeatures and advantages should be or are in any single embodiment.Rather, language referring to the features and advantages may beunderstood to mean that a specific feature, advantage, or characteristicdescribed in connection with an embodiment may be included in at leastone embodiment of the present technology. Thus, discussions of thefeatures and advantages, and similar language, throughout thisspecification may, but do not necessarily, refer to the same embodiment.

Various embodiments of the present disclosure, as discussed above, maybe practiced with steps and/or operations in a different order, and/orwith hardware elements in configurations which are different than thosewhich are disclosed. Therefore, although the technology has beendescribed based upon these example embodiments, it is noted that certainmodifications, variations, and alternative constructions may be apparentand well within the spirit and scope of the technology. Although variousexample embodiments of the present technology are described herein in alanguage specific to structural features and/or methodological acts, thesubject matter defined in the appended claims is not necessarily limitedto the specific features or acts described above. Rather, the specificfeatures and acts described above are disclosed as example forms ofimplementing the claims.

What is claimed is:
 1. A method for video picture intra-predictionestimation, the method comprising: accessing four ‘N×N’ pixel blocks byan intra-prediction estimation device, ‘N’ being an integer value, thefour ‘N×N’ pixel blocks comprising luma-related pixels, and the four‘N×N’ pixel blocks collectively configuring a ‘2N×2N’ pixel block of avideo picture; accessing a first pre-determined number of candidate lumaintra-prediction modes for each of the four ‘N×N’ pixel blocks by theintra-prediction estimation device, a candidacy of the lumaintra-prediction modes being determined based on a predefined measure;identifying, with the intra-prediction estimation device, a presence ofone or more luma intra-prediction modes that are common among thecandidate luma intra-prediction modes of at least two of the four ‘N×N’pixel blocks; and performing, by the intra-prediction estimation device,one of: selecting a principal luma intra-prediction mode for the ‘2N×2N’pixel block from among the one or more luma intra-prediction modes basedon identifying the presence of the one or more luma intra-predictionmodes that are common among the candidate luma intra-prediction modes ofat least two of the four ‘N×N’ pixel blocks, and limiting a partitioningsize to a ‘N×N’ pixel block size for a portion of the video picturecorresponding to the ‘2N×2N’ pixel block subsequent to identifying anabsence of the one or more luma intra-prediction modes that are commonamong the candidate luma intra-prediction modes of at least two of thefour ‘N×N’ pixel blocks.
 2. The method of claim 1, wherein thepredefined measure is one of a sum of absolute differences (SAD) costand a sum of absolute transform differences (SATD) cost.
 3. The methodof claim 1, wherein if a presence of a luma intra-prediction mode fromamong the one or more luma intra-prediction modes that is common to eachof the four ‘N×N’ pixel blocks is identified, then the lumaintra-prediction mode is selected as the principal luma intra-predictionmode for the ‘2N×2N’ pixel block.
 4. The method of claim 1, wherein if apresence of two or more luma intra-prediction modes among the one ormore luma intra-prediction modes that are common to each of the four‘N×N’ pixel blocks is identified, then a luma intra-prediction mode isselected from among the two or more luma intra-prediction modes as theprincipal luma intra-prediction mode for the ‘2N×2N’ pixel block basedon rate distortion optimization (RDO) cost associated with each of thetwo or more luma intra-prediction modes.
 5. The method of claim 1,further comprising performing by the intra-prediction estimation device,if the presence of the one or more luma intra-prediction modes that arecommon among the candidate luma intra-prediction modes of two or three‘N×N’ pixel blocks from among the four ‘N×N’ pixel blocks is identified:associating the one or more luma intra-prediction modes with theremaining pixel blocks from among the four ‘N×N’ pixel blocks; computingRDO cost for each of one or more luma intra-prediction modes for each ofthe remaining pixel blocks; and selecting a luma intra-prediction modefrom among the one or more luma intra-prediction modes as the principalluma intra-prediction mode for the ‘2N×2N’ pixel block based on the RDOcost associated with each of the one or more luma intra-predictionmodes.
 6. The method of claim 1, further comprising: accessing fourpixel blocks comprising chroma-related pixels by the intra-predictionestimation device, the four pixel blocks collectively configuring achroma pixel block corresponding to the ‘2N×2N’ pixel block; accessing asecond pre-determined number of candidate chroma intra-prediction modesfor each of the four pixel blocks by the intra-prediction estimationdevice, a candidacy of the chroma intra-prediction modes beingdetermined based on the predefined measure; identifying, with theintra-prediction estimation device, a presence of one or more chromaintra-prediction modes that are common from among the candidate chromaintra-prediction modes of at least two of the four pixel blocks; andselecting a principal chroma intra-prediction mode for the chroma pixelblock based on identifying the presence of the one or more chromaintra-prediction modes.
 7. The method of claim 6, further comprisingidentifying a presence of the principal luma intra-prediction mode forthe ‘2N×2N’ pixel block from among the one or more chromaintra-prediction modes by the intra-prediction estimation device,wherein the presence of principal luma intra-prediction mode isidentified subsequent to identifying the presence of one or more chromaintra-prediction modes that are common among the candidate chromaintra-prediction modes.
 8. The method of claim 7, wherein if theprincipal luma intra-prediction mode for the ‘2N×2N’ pixel block isidentified to be present from among the one or more chromaintra-prediction modes, then the principal chroma intra-prediction modeis selected from among the one or more chroma intra-prediction modesbased on RDO cost associated with each of the one or more chromaintra-prediction modes.
 9. The method of claim 7, further comprisingperforming by the intra-prediction estimation device, if the principalluma intra-prediction mode for the ‘2N×2N’ pixel block is identified tobe absent from among the one or more chroma intra-prediction modes:associating the principal luma intra-prediction mode with each of thefour pixel blocks; and selecting the principal chroma intra-predictionmode from among the one or more chroma intra-prediction modes and theprincipal luma intra-prediction mode based on RDO cost associated witheach of the one or more chroma intra-prediction modes and the principalluma intra-prediction mode.
 10. The method of claim 6, wherein a pixelblock adjacent to the chroma pixel block is configured to receiveadjusted reconstructed data for performing chroma intra-predictionestimation if a pixel block size corresponding to the chroma pixel blockis chosen as the partitioning size for a portion of the video picturecorresponding to the chroma pixel block.
 11. The method of claim 1,further comprising performing by the intra-prediction estimation devicesubsequent to selecting the principal luma intra-prediction mode:computing a first partitioning cost associated with the ‘2N×2N’ pixelblock based on the selected principal luma intra-prediction mode;comparing the first partitioning cost associated with the ‘2N×2N’ pixelblock with a second partitioning cost associated with four ‘N×N’ pixelblocks collectively; and determining a partitioning size for a portionof the video picture corresponding to the ‘2N×2N’ pixel block based onthe comparison between the first partitioning cost and the secondpartitioning cost.
 12. The method of claim 11, wherein a pixel blockadjacent to the ‘2N×2N’ pixel block is configured to receive adjustedreconstructed data for performing luma intra-prediction estimation if itis determined that the first partitioning cost is less than the secondpartitioning cost.
 13. The method of claim 1, wherein a value of N isone of 8, 16 and
 32. 14. A system for video picture intra-predictionestimation, the system comprising: a memory device configured to storeone or more video pictures; an intra-prediction estimation devicecommunicatively associated with the memory device, the intra-predictionestimation device configured to: access four ‘N×N’ pixel blocks from thememory device, ‘N’ being an integer value, the four ‘N×N’ pixel blockscomprising luma-related pixels, and the four ‘N×N’ pixel blockscollectively configuring a ‘2N×2N’ pixel block of a video picture fromamong the one or more video pictures; access a first pre-determinednumber of candidate luma intra-prediction modes for each of the four‘N×N’ pixel blocks, a candidacy of the luma intra-prediction modes beingdetermined based on a predefined measure; identify a presence of one ormore luma intra-prediction modes that are common among the candidateluma intra-prediction modes of at least two of the four ‘N×N’ pixelblocks; and perform one of: selecting a principal luma intra-predictionmode for the ‘2N×2N’ pixel block from among the one or more lumaintra-prediction modes based on identifying the presence of the one ormore luma intra-prediction modes that are common among the candidateluma intra-prediction modes of at least two of the four ‘N×N’ pixelblocks, and limiting a partitioning size to a ‘N×N’ pixel block size fora portion of the video picture corresponding to the ‘2N×2N’ pixel blocksubsequent to identifying an absence of the one or more lumaintra-prediction modes that are common among the candidate lumaintra-prediction modes of at least two of the four ‘N×N’ pixel blocks.15. The system of claim 14, wherein if a presence of a lumaintra-prediction mode from among the one or more luma intra-predictionmodes that is common to each of the four ‘N×N’ pixel blocks isidentified, then the luma intra-prediction mode is selected as theprincipal luma intra-prediction mode for the ‘2N×2N’ pixel block. 16.The system of claim 14, wherein the intra-prediction estimation deviceis further configured to perform, if the presence of the one or moreluma intra-prediction modes that are common among the candidate lumaintra-prediction modes of two or three ‘N×N’ pixel blocks from among thefour ‘N×N’ pixel blocks is identified: associate the one or more lumaintra-prediction modes with the remaining pixel blocks from among thefour ‘N×N’ pixel blocks; compute RDO cost for each of one or more lumaintra-prediction modes for each of the remaining pixel blocks; andselect a luma intra-prediction mode from among the one or more lumaintra-prediction modes as the principal luma intra-prediction mode forthe ‘2N×2N’ pixel block based on the RDO cost associated with each ofthe one or more luma intra-prediction modes.
 17. The system of claim 14,wherein the intra-prediction estimation device is further configured to:access four pixel blocks comprising chroma-related pixels, the fourpixel blocks collectively configuring a chroma pixel block correspondingto the ‘2N×2N’ pixel block; access a second pre-determined number ofcandidate chroma intra-prediction modes for each of the four pixelblocks, a candidacy of the chroma intra-prediction modes beingdetermined based on the predefined measure; identify a presence of oneor more chroma intra-prediction modes that are common from among thecandidate chroma intra-prediction modes of at least two of the fourpixel blocks; and select a principal chroma intra-prediction mode forthe chroma pixel block based on identifying the presence of the one ormore chroma intra-prediction modes.
 18. The system of claim 17, whereinthe intra-prediction estimation device is further configured to identifya presence of the principal luma intra-prediction mode for the ‘2N×2N’pixel block from among the one or more chroma intra-prediction modes,wherein the presence of principal luma intra-prediction mode isidentified subsequent to identifying the presence of one or more chromaintra-prediction modes that are common among the candidate chromaintra-prediction modes.
 19. A non-transitory computer-readable mediumstoring a set of instructions that when executed cause a computer toperform a method for video picture intra-prediction estimation, themethod comprising: accessing four ‘N×N’ pixel blocks, ‘N’ being aninteger value, the four ‘N×N’ pixel blocks comprising luma-relatedpixels, and the four ‘N×N’ pixel blocks collectively configuring a‘2N×2N’ pixel block of a video picture; accessing a first pre-determinednumber of candidate luma intra-prediction modes for each of the four‘N×N’ pixel blocks, a candidacy of the luma intra-prediction modes beingdetermined based on a predefined measure; identifying a presence of oneor more luma intra-prediction modes that are common among the candidateluma intra-prediction modes of at least two of the four ‘N×N’ pixelblocks; and performing one of: selecting a principal lumaintra-prediction mode for the ‘2N×2N’ pixel block from among the one ormore luma intra-prediction modes based on identifying the presence ofthe one or more luma intra-prediction modes that are common among thecandidate luma intra-prediction modes of at least two of the four ‘N×N’pixel blocks, and limiting a partitioning size to a ‘N×N’ pixel blocksize for a portion of the video picture corresponding to the ‘2N×2N’pixel block subsequent to identifying an absence of the one or more lumaintra-prediction modes that are common among the candidate lumaintra-prediction modes of at least two of the four ‘N×N’ pixel blocks.20. The A non-transitory computer-readable medium of claim 19, whereinif a presence of a luma intra-prediction mode from among the candidateluma intra-prediction modes that is common to each of the four ‘N×N’pixel blocks is identified, then the luma intra-prediction mode isselected as the principal luma intra-prediction mode for the ‘2N×2N’pixel block.